U.S. patent number 10,615,089 [Application Number 15/717,874] was granted by the patent office on 2020-04-07 for composite magnetic sealing material.
This patent grant is currently assigned to TDK CORPORATION. The grantee listed for this patent is TDK Corporation. Invention is credited to Kenichi Kawabata.
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United States Patent |
10,615,089 |
Kawabata |
April 7, 2020 |
Composite magnetic sealing material
Abstract
Disclosed herein is a composite magnetic sealing material
includes a resin material and a filler blended in the resin
material in a blended ratio of 30 vol. % or more to 85 vol. % or
less. The filler includes a magnetic filler containing Fe and 32
wt. % or more and 39 wt. % or less of a metal material contained
mainly of Ni, thereby a thermal expansion coefficient of the
composite magnetic sealing material is 15 ppm/.degree. C. or
less.
Inventors: |
Kawabata; Kenichi (Tokyo,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
TDK Corporation |
Tokyo |
N/A |
JP |
|
|
Assignee: |
TDK CORPORATION (Tokyo,
JP)
|
Family
ID: |
59958926 |
Appl.
No.: |
15/717,874 |
Filed: |
September 27, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180019042 A1 |
Jan 18, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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15351701 |
Nov 15, 2016 |
9818518 |
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62315860 |
Mar 31, 2016 |
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Foreign Application Priority Data
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Oct 27, 2016 [JP] |
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2016-210146 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
23/295 (20130101); H01L 23/552 (20130101); H01F
1/14758 (20130101); H01L 23/10 (20130101); H01L
2924/351 (20130101); H01L 2924/3025 (20130101); H01L
2924/3511 (20130101); H01L 23/3121 (20130101); H01L
2924/14 (20130101); H01L 2924/35121 (20130101) |
Current International
Class: |
H01L
23/10 (20060101); H01F 1/147 (20060101); H01L
23/552 (20060101); H01L 23/31 (20060101); H01L
23/29 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1357056 |
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Feb 2003 |
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CN |
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H01-283900 |
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Nov 1989 |
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JP |
|
H02-078299 |
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Mar 1990 |
|
JP |
|
05-005162 |
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Jan 1993 |
|
JP |
|
H10-064714 |
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Mar 1998 |
|
JP |
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H11214592 |
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Jun 1999 |
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JP |
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11-297556 |
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Oct 1999 |
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JP |
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2001-303111 |
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Oct 2001 |
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JP |
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2004-207322 |
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Jul 2004 |
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JP |
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2005-347499 |
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Dec 2005 |
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JP |
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2010-087058 |
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Apr 2010 |
|
JP |
|
2013-229354 |
|
Nov 2013 |
|
JP |
|
2014-127624 |
|
Jul 2014 |
|
JP |
|
Primary Examiner: Koslow; C Melissa
Attorney, Agent or Firm: Young Law Firm, P.C.
Claims
What is claimed is:
1. A composite magnetic sealing material comprising: a resin
material; and a magnetic filler blended in the resin material, the
magnetic filler containing Fe and 32 wt. % or more and 39 wt. % or
less of a metal material composed mainly of Ni.
2. The composite magnetic sealing material as claimed in claim 1,
wherein the metal material further contains 0.1 wt. % or more and 8
wt. % or less of Co relative to a total weight of the magnetic
filler.
3. The composite magnetic sealing material as claimed in claim 1,
further comprising a non-magnetic filler blended in the resin
material.
4. The composite magnetic sealing material as claimed in claim 3,
wherein a ratio of an amount of the non-magnetic filler relative to
a sum of an amounts of the magnetic filler and the non-magnetic
filler is 1 vol. % or more and 40 vol. % or less.
5. The composite magnetic sealing material as claimed in claim 3,
wherein a blended ratio of the magnetic filler and the non-magnetic
filler in the resin material is 50 vol. % or more and 85 vol. % or
less.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a composite magnetic sealing
material and, more particularly, to a composite magnetic sealing
material suitably used as a molding material for electronic circuit
package.
Description of Related Art
In recent years, an electronic device such as a smartphone is
equipped with a high-performance radio communication circuit and a
high-performance digital chip, and an operating frequency of a
semiconductor IC used therein tends to increase. Further, adoption
of an SIP (System-In Package) having a 2.5D or 3D structure, in
which a plurality of semiconductor ICs are connected by a shortest
wiring, is accelerated, and modularization of a power supply system
is expected to accelerate. Further, an electronic circuit module
having a large number of modulated electronic components
(collective term of components, such as passive components (an
inductor, a capacitor, a resistor, a filter, etc.), active
components (a transistor, a diode, etc.), integrated circuit
components (an semiconductor IC, etc.) and other components
required for electronic circuit configuration) is expected to
become more and more popular, and an electronic circuit package
which is a collective term for the above SIP, electronic circuit
module, and the like tends to be mounted in high density along with
sophistication, miniaturization, and thinning of an electronic
device such as a smartphone. However, this tendency poses a problem
of malfunction and radio disturbance due to noise. The problem of
malfunction and radio disturbance is difficult to be solved by
conventional noise countermeasure techniques. Thus, recently,
self-shielding of the electronic circuit package has become
accelerated, and an electromagnetic shielding using a conductive
paste or a plating or sputtering method has been proposed and put
into practical use, and higher shielding characteristics are
required in the future.
To achieve this, recently, there are proposed electronic circuit
packages in which a molding material itself has magnetic shielding
characteristics. For example, Japanese Patent Application Laid-Open
No. H10-64714 discloses a composite magnetic sealing material added
with soft magnetic powder having an oxide film as a molding
material for electronic circuit package.
However, conventional composite magnetic sealing materials have a
drawback in that it has a large thermal expansion coefficient.
Thus, a mismatch occurs between a composite magnetic sealing
material and a package substrate or electronic components in terms
of the thermal expansion coefficient. As a result, an aggregated
substrate having a strip shape after molding may be greatly warped,
or there may occur a warp large enough to cause a problem with
connectivity of an electronic circuit package in a diced state in
mounting reflow. This phenomenon will be described in detail
below.
In recent years, various structures have been proposed for and
actually put into practical use as a semiconductor package or an
electronic component module, and, currently, there is generally
adopted a structure in which electronic components such as
semiconductor ICs are mounted on an organic multilayer substrate,
followed by molding of the upper portion and periphery of the
electronic component package by a resin sealing material. A
semiconductor package or electronic component module having such a
structure is molded as an aggregated substrate, followed by
dicing.
In this structure, an organic multilayer substrate and a resin
sealing material having different physical properties constitute a
so-called bimetal, so that a warp may occur due to the difference
between thermal expansion coefficients, glass transition, or curing
shrinkage of a molding material. To suppress the warp, it is
necessary to make the physical properties such as thermal expansion
coefficients coincide with each other as much as possible. In
recent years, an organic multilayer substrate used for a
semiconductor package or an electronic circuit module is getting
thinner and thinner and is increasing in the number of layers
thereof to meet requirements for height reduction. In order to
realize high rigidity and low thermal expansion for ensuring good
handleability of a thin substrate while achieving the thickness
reduction and multilayer structure, use of a substrate material
having a high glass transition temperature, addition of a filler
having a small thermal expansion coefficient to a substrate
material, or use of glass cloth having a smaller thermal expansion
coefficient is a common practice at present.
On the other hand, the difference in physical properties between
semiconductor ICs and electronic components mounted on a substrate
and a molding material also generates a stress, causing various
problems such as interfacial delamination of the molding material
and crack of the electronic components or molding material.
Incidentally, silicon is used as the semiconductor ICs. The thermal
expansion coefficient of silicon is 3.5 ppm/.degree. C., and that
of a baked chip component such as a ceramic capacitor or an
inductor is about 10 ppm/.degree. C.
Thus, the molding material is also required to have a small thermal
expansion coefficient, and some commercially-available materials
have a thermal expansion coefficient below 10 ppm/.degree. C. As a
method for reducing the thermal expansion coefficient of the
molding material, adopting an epoxy resin having a small thermal
expansion coefficient, as well as, blending fused silica having a
very small thermal expansion coefficient of 0.5 ppm/.degree. C. in
a sealing resin at a high filling rate can be taken.
General magnetic materials have a high thermal expansion
coefficient. Thus, as described in Japanese Patent Application
Laid-Open No. H10-64714, the composite magnetic sealing material
obtained by adding general soft magnetic powder to a mold resin
cannot achieve a target small thermal expansion coefficient.
SUMMARY
An object of the present invention is therefore to provide a
composite magnetic sealing material having a small thermal
expansion coefficient.
A composite magnetic sealing material according to the present
invention includes a resin material and a filler blended in the
resin material in a blended ratio of 30 vol. % or more to 85 vol. %
or less. The filler includes a magnetic filler containing Fe and 32
wt. % or more and 39 wt. % or less of a metal material contained
mainly of Ni, thereby a thermal expansion coefficient of the
composite magnetic sealing material is 15 ppm/.degree. C. or
less.
According to the present invention, the thermal expansion
coefficient of the composite magnetic sealing material can be
reduced to 15 ppm/.degree. C. or less by using the magnetic filler
having a small thermal expansion coefficient. Thus, when the
composite magnetic sealing material according to the present
invention is used as a molding material for an electronic circuit
package, it is possible to prevent the warp of the substrate,
interfacial delamination or crack of a molding material.
In the present invention, the metal material may further contain
0.1 wt. % or more and 8 wt. % or less of Co relative to the total
weight of the magnetic filler. This enables a further reduction in
the thermal expansion coefficient of the composite magnetic sealing
material.
In the present invention, the filler may further include a
non-magnetic filler. This enables a further reduction in the
thermal expansion coefficient of the composite magnetic sealing
material. In this case, the ratio of the amount of the non-magnetic
filler relative to the sum of the amounts of the magnetic filler
and the non-magnetic filler is preferably 1 vol. % or more and 40
vol. % or less. This enables a further reduction in the thermal
expansion coefficient of the composite magnetic sealing material
while ensuring sufficient magnetic characteristics. In this case,
the non-magnetic filler preferably contains at least one material
selected from the group consisting of SiO.sub.2, ZrW.sub.2O.sub.8,
(ZrO).sub.2P.sub.2O.sub.7, KZr.sub.2(PO.sub.4).sub.3, or
Zr.sub.2(WO.sub.4)(PO.sub.4).sub.2. These materials have a very
small or negative thermal expansion coefficient, thus enabling a
further reduction in the thermal expansion coefficient of the
composite magnetic sealing material.
In the present invention, the magnetic filler preferably has a
substantially spherical shape. This enables an increase in the
ratio of the magnetic filler to the composite magnetic sealing
material.
In the present invention, the surface of the magnetic filler is
preferably insulatively coated, and the film thickness of the
insulating coating is preferably 10 nm or more. With this
configuration, the volume resistivity of the composite magnetic
sealing material can be increased to, e.g., 10.sup.10 .OMEGA.cm or
more, making it possible to ensure insulating performance required
for a molding material for an electronic circuit package.
In the present invention, the resin material is preferably a
thermosetting resin material, and the thermosetting resin material
preferably contains at least one material selected from the group
consisting of an epoxy resin, a phenol resin, a urethane resin, a
silicone resin, or an imide resin.
As described above, the composite magnetic sealing material
according to the present invention has a small thermal expansion
coefficient. Thus, when the composite magnetic sealing material is
used as a sealing material for an electronic circuit package, it is
possible to prevent the warp of the substrate, interfacial
delamination or crack of a molding material.
BRIEF DESCRIPTION OF THE DRAWINGS
The above features and advantages of the present invention will be
more apparent from the following description of certain preferred
embodiments taken in conjunction with the accompanying drawings, in
which:
FIG. 1 is a schematic view for explaining a configuration of a
composite magnetic sealing material according to a preferred
embodiment of the present invention;
FIG. 2 is a graph illustrating the relationship between the Ni
ratio of the magnetic filler and the thermal expansion coefficient
and the magnetic permeability of the composite magnetic sealing
material;
FIG. 3 is a graph illustrating the relationship between the Ni
ratio of the magnetic filler and the thermal expansion coefficient
of the composite magnetic sealing material;
FIG. 4 is a graph illustrating the relationship between the Ni
ratio of the magnetic filler and the magnetic permeability of the
composite magnetic sealing material;
FIG. 5 is a graph illustrating the relationship between the Co
ratio of the magnetic filler and the thermal expansion coefficient
and magnetic permeability of the composite magnetic sealing
material;
FIG. 6 is a graph illustrating the relationship between the
additive ratio of the non-magnetic filler and the thermal expansion
coefficient of the composite magnetic sealing material;
FIG. 7 is a graph illustrating the relationship between the
presence/absence of the insulating coat formed on the surface of
the magnetic filler and volume resistivity;
FIG. 8 is a graph illustrating the relationship between the film
thickness of the insulating coat formed on the surface of the
magnetic filler and volume resistivity;
FIG. 9 is a graph illustrating the relationship between the volume
resistivity of the magnetic filler 6 and that of the composite
magnetic sealing material 2.
FIGS. 10A and 10B are schematic cross-sectional views illustrating
a structure of an electronic circuit package using the composite
magnetic sealing material;
FIG. 11 is a graph illustrating noise attenuation in the electronic
circuit package shown in FIG. 10B;
FIGS. 12 to 14 are graphs each illustrating the relationship
between the film thickness of the metal film included in the
electronic circuit package shown in FIG. 10B and noise
attenuation;
FIGS. 15 and 16 are graphs illustrating the warp amount of the
substrate during temperature rising and that during temperature
dropping in the electronic circuit packages shown in FIGS. 10A and
10B;
FIG. 17 is a table indicating compositions 1 to 3; and
FIGS. 18 and 19 are tables indicating measurement results of the
Examples.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Preferred embodiments of the present invention will be explained
below in detail with reference to the accompanying drawings.
FIG. 1 is a schematic view for explaining a configuration of a
composite magnetic sealing material according to a preferred
embodiment of the present invention.
As illustrated in FIG. 1, a composite magnetic sealing material 2
according to the present embodiment includes a resin material 4,
and a magnetic filler 6 and a non-magnetic filler 8 which are
blended in the resin material 4. Although not especially limited,
the resin material 4 is preferably composed mainly of a
thermosetting resin material. Specifically, the resin material 4 is
preferably composed mainly of an epoxy resin, a phenol resin, a
urethane resin, a silicone resin, or an imide resin and more
preferably uses a base resin and a curing agent used for an epoxy
resin-based or a phenol resin-based semiconductor sealing
material.
The most preferable is the epoxy resin having a reactive epoxy
group at its terminal, which can be combined with various types of
curing agents and curing accelerators. Examples of the epoxy resin
include a bisphenol A epoxy resin, a bisphenol F epoxy resin, a
phenoxy type epoxy resin, a naphthalene type epoxy resin, a
multifunctional-type epoxy resin (dicyclopentadiene type epoxy
resin, etc.), a biphenyl-type (bifunctional) epoxy resin, and an
epoxy resin having a special structure. Among them, the biphenyl
type epoxy resin, naphthalene type epoxy resin, and
dicyclopentadiene type epoxy resin are useful since they can attain
low thermal expansion. Examples of the curing agent or curing
accelerator include amine-based compound alicyclic diamine,
aromatic diamine, other amine-based compounds (imidazole, tertiary
amine, etc.), an acid anhydride compound (high-temperature curing
agent, etc.), a phenol resin (novolac type phenol resin, cresol
novolac type phenol resin, etc.), an amino resin, dicyandiamide,
and a Lewis acid complex compound. For material kneading, known
means such as a kneader, three-roll mills, or a mixer may be
used.
The magnetic filler 6 is formed of an Fe--Ni based material and
contains 32 wt. % or more and 39 wt. % or less of a metal material
composed mainly of Ni. The remaining 61-68 wt. % is Fe. The
blending ratio of the magnetic filler 6 to the composite magnetic
sealing material 2 is 30 vol. % or more and 85 vol. % or less. When
the blending ratio of the magnetic filler 6 is less than 30 vol. %,
it is difficult to obtain sufficient magnetic characteristics; on
the other hand, when the blending ratio of the magnetic filler 6
exceeds 85 vol. %, it is difficult to ensure characteristics, such
as flowability, required for a sealing material.
The metal material composed mainly of Ni may contain a small amount
of Co. That is, a part of Ni may be substituted by Co. The
containment of Co enables a further reduction in the thermal
expansion coefficient of the composite magnetic sealing material 2.
The adding amount of Co to the composite magnetic sealing material
2 is preferably 0.1 wt. % or more and 8 wt. % or less.
The shape of the magnetic filler 6 is not especially limited.
However, the magnetic filler 6 may preferably be formed into a
spherical shape for high packing density. Further, fillers of
different particle sizes may be blended as the magnetic filler 6
for closest packing. Further, forming the magnetic filler 6 into a
spherical shape (or substantially a spherical shape) enables a
reduction in damage to electronic components during molding.
Particularly, for high packing density or closest packing, the
shape of the magnetic filler 6 is preferably a true sphere. The
magnetic filler 6 preferably has a high tap density and a small
specific surface area. As a formation method for the magnetic
filler 6, there are known a water atomization method, a gas
atomization method, and a centrifugal disc atomization method.
Among them, the gas atomization method is most preferable since it
can achieve a high tap density and reduce the specific surface
area.
Although not especially limited, the surface of the magnetic filler
6 is covered with an insulating coat 7 formed of an oxide of metal
such as Si, Al, Ti, or Mg or an organic material for enhancement of
flowability, adhesion, and insulation performance. To sufficiently
enhance the volume resistivity of the composite magnetic sealing
material 2, the film thickness of the insulating coat 7 is
preferably set to 10 nm or more. The insulating coat 7 may be
achieved by coating a thermosetting material on the surface of the
magnetic filler 6 or may be achieved by formation of an oxide film
by hydration of metal alkoxide such as tetraethyloxysilane or
tetraemthyloxysilane and, most preferably, it is achieved by
formation of a silicon oxide coating film. Further, more
preferably, organofunctional coupling treatment is applied to the
insulating coat 7.
The composite magnetic sealing material 2 according to the present
embodiment contains the non-magnetic filler 8. As the non-magnetic
filler 8, a material having a smaller thermal expansion coefficient
than that of the magnetic filler 6, such as SiO.sub.2,
ZrW.sub.2O.sub.8, (ZrO).sub.2P.sub.2O.sub.7,
KZr.sub.2(PO.sub.4).sub.3, or Zr.sub.2(WO.sub.4)(PO.sub.4).sub.2,
or a material having a negative thermal expansion coefficient is
preferably used. By adding the non-magnetic filler 8 to the
composite magnetic sealing material 2, it is possible to further
reduce the thermal expansion coefficient. Further, the following
materials may be added to the composite magnetic sealing material
2: flame retardant such as aluminum oxide or magnesium oxide;
carbon black, pigment, or dye for coloring; surface-treated
nanosilica having a particle diameter of 100 nm or less for
enhancement of slidability, flowability, and
dispersibility/kneadability; and a wax component for enhancement of
mold releasability. It is not essential that the composite magnetic
sealing material according to the present invention contains the
non-magnetic filler.
Further, organofunctional coupling treatment may be applied to the
surface of the magnetic filler 6 or surface of the non-magnetic
filler 8 for enhancement of adhesion and flowability. The
organofunctional coupling treatment may be performed using a known
wet or dry method, or by an integral blend method. Further, the
surface of the magnetic filler 6 or surface of the non-magnetic
filler 8 may be coated with a thermosetting resin for enhancement
of wettability.
When the non-magnetic filler 8 is added, the ratio of the amount of
the non-magnetic filler 8 relative to the sum of the amounts of the
magnetic filler 6 and the non-magnetic filler 8 is preferably 1
vol. % or more and 40 vol. % or less. In other words, 1 vol. % or
more and 40 vol. % or less of the magnetic filler 6 can be
substituted by the non-magnetic filler 8. When the additive amount
of the non-magnetic filler 8 is less than 1 vol. %, addition effect
of the non-magnetic filler 8 is hardly obtained; on the other hand,
when the additive amount of the non-magnetic filler 8 exceeds 40
vol. %, the relative amount of the magnetic filler 6 is too small,
resulting in difficulty in providing sufficient magnetic
characteristics.
The composite magnetic sealing material 2 may be a liquid or solid,
depending on selection of a base resin and a curing agent according
to the molding method therefor. The composite magnetic sealing
material 2 in a solid state may be formed into a tablet shape for
transfer molding and into a granular shape for injection molding or
compression molding. The molding method using the composite
magnetic sealing material 2 may be appropriately selected from
among the followings: transfer molding; compression molding;
injection molding; cast molding; vacuum cast molding; vacuum
printing; printing; dispensing; and a method using a slit nozzle. A
molding condition may be appropriately selected from combinations
of the base resin, curing agent and curing accelerator to be used.
Further, after-cure treatment may be applied as needed after the
molding.
FIG. 2 is a graph illustrating the relationship between the Ni
ratio of the magnetic filler 6 and the thermal expansion
coefficient and the magnetic permeability of the composite magnetic
sealing material 2. The graph of FIG. 2 represents a case where the
magnetic filler 6 is composed of substantially only Fe and Ni.
Here, it is assumed that the additive amount of the magnetic filler
6 relative to the composite magnetic sealing material 2 is 70 vol.
% and no non-magnetic filler 8 is added to the composite magnetic
sealing material 2.
As illustrated in FIG. 2, when the Ni ratio of the magnetic filler
6 is 32 wt. % or more and 39 wt. % or less, the thermal expansion
coefficient of the composite magnetic sealing material 2 is
remarkably reduced (it may be reduced to 10 ppm/.degree. C. in some
conditions). In the example of FIG. 2, the smallest thermal
expansion coefficient (about 9.3 ppm/.degree. C.) is obtained when
the Ni ratio is about 35 wt. %. On the other hand, the magnetic
permeability is not strongly correlated to the Ni ratio, and .mu.
is 12 to 13 in the range of the Ni ratio illustrated in FIG. 2.
The reason that such characteristics are obtained is that invar
characteristics where volumetric changes due to thermal expansion
and magnetic distortion cancel out each other is exhibited when the
Ni ratio falls within the above range. A material where the invar
characteristic is exhibited is called an invar material, which is
known as a material for a die requiring high precision; however, it
was not used as a material for the magnetic filler to be blended in
a composite magnetic sealing material. The present inventor pays
attention to the magnetic characteristics and small thermal
expansion coefficient that the invar material has and uses the
invar material as a material for the magnetic filler and thereby
realize the composite magnetic sealing material 2 having a small
thermal expansion coefficient.
FIG. 3 is a graph illustrating the relationship between the Ni
ratio of the magnetic filler 6 and the thermal expansion
coefficient of the composite magnetic sealing material 2. The graph
of FIG. 3 represents a case where the magnetic filler 6 is composed
substantially of only Fe and Ni. Here, it is assumed that the
additive amount of the magnetic filler 6 relative to the composite
magnetic sealing material 2 is 50 vol. %, 60 vol. %, or 70 vol. %
and no non-magnetic filler 8 is added to the composite magnetic
sealing material 2.
As illustrated in FIG. 3, even in a case where the additive amount
of the magnetic filler 6 is either 50 vol. %, 60 vol. %, or 70 vol.
%, when the Ni ratio of the magnetic filler 6 is 32 wt. % or more
and 39 wt. % or less, the thermal expansion coefficient of the
composite magnetic sealing material 2 is remarkably reduced. The
more the additive amount of the magnetic filler 6 is, the smaller
the thermal expansion coefficient. Therefore, when the additive
amount of the magnetic filler 6 is small (e.g., 30 vol. %), the
non-magnetic filler 8 formed of fused silica is further added to
reduce the thermal expansion coefficient of the composite magnetic
sealing material 2 to 15 ppm/.degree. C. or less. Specifically, by
setting the total additive amount of the magnetic filler 6 and the
non-magnetic filler 8 to 50 vol. % or more and 85 vol. % or less,
the thermal expansion coefficient of the composite magnetic sealing
material 2 can be sufficiently reduced (e.g., to 15 ppm/.degree. C.
or less).
FIG. 4 is a graph illustrating the relationship between the Ni
ratio of the magnetic filler 6 and the magnetic permeability of the
composite magnetic sealing material 2. As in the case of the graph
of FIG. 3, the graph of FIG. 4 represents a case where the magnetic
filler 6 is composed substantially of only Fe and Ni and the
additive amount of the magnetic filler 6 relative to the composite
magnetic sealing material 2 is 50 vol. %, 60 vol. %, or 70 vol. %,
and no non-magnetic filler 8 is added to the composite magnetic
sealing material 2.
As illustrated in FIG. 4, even in a case where the additive amount
of the magnetic filler 6 is either 50 vol. %, 60 vol. %, or 70 vol.
%, the Ni ratio and the magnetic permeability are not strongly
correlated to each other. The more the additive amount of the
magnetic filler 6 is, the larger the magnetic permeability.
FIG. 5 is a graph illustrating the relationship between the Co
ratio of the magnetic filler 6 and the thermal expansion
coefficient and magnetic permeability of the composite magnetic
sealing material 2. The graph of FIG. 5 represents a case where the
sum of the amounts of Ni and Co contained in the magnetic filler 6
is 37 wt. %, the additive amount of the magnetic filler 6 relative
to the composite magnetic sealing material 2 is 70 vol. %, and no
non-magnetic filler 8 is added to the composite magnetic sealing
material 2.
As illustrated in FIG. 5, as compared to a case where Co is not
contained (Co=0 wt. %) in the magnetic filler 6, the thermal
expansion coefficient of the composite magnetic sealing material 2
is further reduced when Ni constituting the magnetic filler 6 is
substituted by 8 wt. % or less of Co. However, when the substituted
amount by Co is 10 wt. %, the thermal expansion coefficient is
conversely increased. Therefore, the additive amount of Co relative
to the magnetic filler 6 is preferably 0.1 wt. % or more and 8 wt.
% or less.
FIG. 6 is a graph illustrating the relationship between the
additive ratio of the non-magnetic filler 8 and the thermal
expansion coefficient of the composite magnetic sealing material 2.
The graph of FIG. 6 represents a case where the sum of the amounts
of the magnetic filler 6 and the non-magnetic filler 8 is 70 vol.
%, the magnetic filler 6 is composed of 64 wt. % of Fe and 36 wt. %
of Ni, and the non-magnetic filler 8 is formed of SiO.sub.2.
As illustrated in FIG. 6, as the ratio of the amount of the
non-magnetic filler 8 is increased, the thermal expansion
coefficient of the composite magnetic sealing material 2 is
reduced; however, when the amount of the non-magnetic filler 8
exceeds 40 vol. % relative to 60 vol. % of the magnetic filler 6,
thermal expansion coefficient reduction effect is nearly saturated.
Thus, the amount of the non-magnetic filler 8 relative to the sum
of the amounts of the magnetic filler 6 and non-magnetic filler 8
is preferably 1 vol. % or more and 40 vol. % or less.
FIG. 7 is a graph illustrating the relationship between the
presence/absence of the insulating coat 7 formed on the surface of
the magnetic filler 6 and volume resistivity. Two compositions are
prepared as a material for the magnetic filler 6 as follows:
composition A (Fe=64 wt. %, Ni=36 wt. %); and composition B (Fe=63
wt. %, Ni=32 wt. %, Co=5 wt. %). The insulating coat 7 is formed of
SiO.sub.2 having a thickness of 40 nm. The magnetic filler 6 of
either the composition A or composition B has a cut diameter of 32
.mu.m and a particle diameter D50 of 20 .mu.m.
As illustrated in FIG. 7, in both the composition A and composition
B, coating with the insulating coat 7 significantly increases the
volume resistivity of the magnetic filler 6. In addition, the
coating with the insulating coat 7 reduces pressure dependency of
the magnetic filler 6 at the time of measurement.
FIG. 8 is a graph illustrating the relationship between the film
thickness of the insulating coat 7 formed on the surface of the
magnetic filler 6 and volume resistivity. The graph of FIG. 8
represents a case where the magnetic filler 6 is composed of 64 wt.
% of Fe and 36 wt. % of Ni. The particle diameter of the magnetic
filler 6 is equal to the particle diameter of the magnetic filler 6
in the example of FIG. 7.
As illustrated in FIG. 8, by coating the magnetic filler 6 with the
insulating coat 7 having a film thickness of 10 nm or more, the
volume resistivity of the magnetic filler 6 is increased. In
particular, when the magnetic filler 6 is coated with the
insulating coat 7 having a film thickness of 30 nm or more, a very
high volume resistivity can be obtained regardless of an applied
pressure at the time of measurement.
FIG. 9 is a graph illustrating the relationship between the volume
resistivity of the magnetic filler 6 and that of the composite
magnetic sealing material 2.
As illustrated in FIG. 9, the volume resistivity of the magnetic
filler 6 and that of the composite magnetic sealing material 2 are
in proportion to each other. In particular, when the volume
resistivity of the magnetic filler 6 is 10.sup.5 .OMEGA.cm or more,
the volume resistivity of the composite magnetic sealing material 2
can be increased to 10.sup.10 .OMEGA.cm or more. When the composite
magnetic sealing material 2 having a volume resistivity of
10.sup.10 .OMEGA.cm or more is used as a molding material for
electronic circuit package, a sufficient insulating performance can
be ensured.
FIG. 10A is a schematic cross-sectional view illustrating a
structure of an electronic circuit package 10A using the composite
magnetic sealing material 2. FIG. 10B is a schematic
cross-sectional view illustrating a structure of an electronic
circuit package 10B using the composite magnetic sealing material
2.
The electronic circuit package 10A illustrated in FIG. 10A includes
a substrate 20, an electronic component 30 mounted on the substrate
20, and a magnetic mold resin 40 that covers a surface 21 of the
substrate 20 so as to embed the electronic component 30 therein.
The magnetic mold resin 40 is formed of the composite magnetic
sealing material 2. The electronic circuit package 10B differs from
the electronic circuit package 10A in that it further includes a
metal film 60 that covers an upper surface 41 and a side surface 42
of the magnetic mold resin 40 and covers a side surface 27 of the
substrate 20. In both the electronic circuit packages 10A and 10B,
the substrate 20 has a thickness of 0.25 mm, and the magnetic mold
resin 40 has a thickness of 0.50 mm.
FIG. 11 is a graph illustrating noise attenuation in the electronic
circuit package 10B. The metal film 60 is composed of a laminated
film of Cu and Ni, and two types of metal films 60 whose Cu films
have different thicknesses are evaluated. Specifically, the metal
film 60 of sample A has a configuration in which the Cu film having
a thickness of 4 .mu.m and the Ni film having a thickness of 2
.mu.m are laminated, and the metal film 60 of sample B has a
configuration in which the Cu film having a thickness of 7 .mu.m
and the Ni film having a thickness of 2 .mu.m are laminated. For
comparison, values of samples C and D each formed by using a
molding material not containing the magnetic filler 6 are also
shown. The metal film 60 of sample C has a configuration in which
the Cu film having a thickness of 4 .mu.m and the Ni film having a
thickness of 2 .mu.m are laminated, and the metal film 60 of sample
D has a configuration in which the Cu film having a thickness of 7
.mu.m and the Ni film having a thickness of 2 .mu.m are
laminated.
As illustrated in FIG. 11, when the composite magnetic sealing
material 2 containing the magnetic filler 6 is used, noise
attenuation effect is enhanced especially at a frequency band of
100 MHz or less as compared to a case where the molding material
not containing the magnetic filler 6 is used. Further, it can be
seen that the larger the thickness of the metal film 60, the higher
the noise attenuation performance.
FIGS. 12 to 14 are graphs each illustrating the relationship
between the film thickness of the metal film 60 included in the
electronic circuit package 10B and noise attenuation. FIG. 12, FIG.
13, and FIG. 14 illustrate the noise attenuation in the frequency
bands of 20 MHz, 50 MHz, and 100 MHz, respectively. For comparison,
a value obtained when a molding material not containing the
magnetic filler 6 is also shown.
As illustrated, in all the frequency bands of FIGS. 12 to 14, the
larger the thickness of the metal film 60, the higher the noise
attenuation performance. Further, by using the composite magnetic
sealing material 2 containing the magnetic filler 6, it is possible
to obtain higher noise attenuation performance in all the frequency
bands of FIGS. 12 to 14, than in a case where a molding material
not containing the magnetic filler 6.
FIG. 15 is a graph illustrating the warp amount of the substrate 20
during temperature rising and that during temperature dropping in
the electronic circuit packages 10A and 10B. For comparison, values
obtained when the magnetic filler 6 is substituted by the
non-magnetic filler formed of SiO.sub.2 are shown in FIG. 16.
As illustrated in FIG. 15, the warp amount of the substrate 20
caused due to a temperature change is smaller in the electronic
circuit package 10B having the metal film 60 than in the electronic
circuit package 10A not having the metal film 60. Further, as is
clear from a comparison between FIGS. 15 and 16, the warp
characteristics of the respective electronic circuit packages 10A
and 10B using the composite magnetic sealing material 2 containing
the magnetic filler 6 are substantially equivalent to the warp
characteristics of the respective electronic circuit packages 10A
and 10B using a molding material containing the non-magnetic filler
formed of SiO.sub.2.
While the preferred embodiments of the present invention have been
described, the present invention is not limited thereto. Thus,
various modifications may be made without departing from the gist
of the invention, and all of the modifications thereof are included
in the scope of the present invention.
EXAMPLES
<Production of Composite Magnetic Sealing Material>
A resin material was prepared with 830S (bisphenol A epoxy resin)
made by Dainippon Ink & Chemicals, Inc., used as a base resin,
with 0.5 equivalent of dicyandiamide made by Nippon Carbide
Industries Co., Inc. added to the base resin as a curing agent, and
with 1 wt. % of C11Z-CN (imidazole) made by Shikoku Chemicals
Corporation added to the base resin as a curing accelerator.
50 vol. %, 60 vol. %, or 70 vol. % of a magnetic filler having the
composition illustrated in FIG. 17 was added to the above resin
material, followed by intensive kneading to obtain a paste. If
pasting failed, butylcarbitol acetate was added appropriately. The
obtained paste was coated to a thickness of about 300 .mu.m and
then heat-cured sequentially at 100.degree. C. for one hour, at
130.degree. C. for one hour, at 150.degree. C. for one hour, and at
180.degree. C. for one hour in this order, to obtain a cured sheet.
The composition 1 (comparative example) is a magnetic material
generally called PB Permalloy.
<Measurement of Thermal Expansion Coefficient>
The above cured sheet was cut to a length of 12 mm and a width of 5
mm. Then, TMA was used to raise temperature from room temperature
to 200.degree. C. at 5.degree. C./min, and a thermal expansion
coefficient was calculated from the amount of expansion in a
temperature range of 50.degree. C. to 100.degree. C. which is lower
than a glass transition temperature. The measurement results are
shown in FIG. 18. In FIG. 18, the measurement result obtained when
the non-magnetic filler formed of SiO.sub.2 is used in place of the
magnetic filler is also shown.
As illustrated in FIG. 18, when the magnetic filler having the
composition 2 or 3 is used, the thermal expansion coefficient is
significantly reduced as compared to when the magnetic filler
having the composition 1 (comparative example) is used. In
particular, when the additive amount is 60 vol. % or more, a
thermal expansion coefficient equivalent to that obtained when the
non-magnetic filler formed of SiO.sub.2 is used is obtained, and
when the additive amount is 70 vol. %, the thermal expansion
coefficient is as small as 10 ppm/.degree. C. or less.
<Measurement of Magnetic Permeability>
The above cured sheet was cut into a ring shape having an outer
diameter of 7.9 mm and an inner diameter of 3.1 mm. Then, the
material analyzer function of impedance analyzer E4991 manufactured
by Agilent Corp., Ltd. was used to measure an effective magnetic
permeability (.mu.') at 10 MHz. The measurement results are shown
in FIG. 19.
As illustrated in FIG. 19, the magnetic permeability obtained when
the magnetic filler having the composition 2 or 3 is substantially
equivalent to the magnetic permeability obtained when the magnetic
filler having the composition 1 (Comparative Example) is used.
<Considerations>
The composite magnetic sealing material obtained by adding the
magnetic filler having the composition 2 or 3 to a resin material
has a thermal expansion coefficient equivalent to the thermal
expansion coefficient obtained when the non-magnetic filler formed
of SiO.sub.2 is used and has a magnetic permeability equivalent to
the magnetic permeability obtained when the magnetic filler formed
of PB permalloy is used. Thus, by using, as a sealing material for
an electronic circuit package, the composite magnetic sealing
material obtained by adding the magnetic filler having the
composition 2 or 3 to a resin material, it is possible to obtain
excellent magnetic shielding characteristics while preventing the
warp of the substrate, interfacial delamination or crack of a
molding material.
* * * * *